ABSTRACT
The fundamental definition of concertedness is the requirement of a single transition state between reactant and product and the subsidiary definition is based on the bond order in the bonds undergoing major transformation. The study of concertedness essentially devolves into one of demonstrating the absence or existence of intermediates. A cornerstone of techniques for mechanism in organic chemistry is that an inline concerted mechanism for displacement at an aliphatic centre requires inversion of configuration at the central carbon atom. Intermediates can be detected by observation of positional isotope exchange in reactions which can be associative or dissociative. Isotopic probes can be used to determine the strengths of each major bonding change for the transition state structure and could therefore provide evidence regarding the timing of the bonding changes in the overall mechanism. Molecular mechanics allows calculation of isotope effects over a range of bonding parameters and the matrix of results is compared with a set of experimental isotope effects.
